The in situ density of compacted layers obtained from sand-cone test is commonly used to assess the quality of compaction of pavement layers. This test is tedious, time consuming, and sometimes not feasible to perform in accordance with specifications. In this study, a lightweight deflectometer (LWD) is used to measure the modulus of deformation, ELWD, of pavement layers and to perform the quality control (QC) of pavement layers. An extensive LWD field testing program was undertaken on 95 test locations of an expressway along the outer ring road located in Hyderabad, India, and the ELWD values of the compacted base and surface layers were commonly found to range from 45 to 60 MPa and 105 to 120 MPa, respectively. The coefficient of variation of the ELWD of base and surface layers was found to range from 4 to 12%. Finite-element analysis was also carried out to study the effect of bottom pavement layers on measured ELWD values from LWD testing. The results showed that the top stiff layer absorbs a significant portion of the load applied on the surface of the layered pavement system, indicating that the ELWD obtained from LWD testing is affected predominantly by the top stiff layer. Finally, a case study on a low-volume road is presented to demonstrate the relationship between the LWD modulus of deformation and in situ density obtained from a sand-cone test. The LWD device was found to provide quick test results and simple to operate on any pavement layer, and hence the frequency of QC tests can be increased, leading to an improvement in the overall quality of compacted pavement layers and, thus, pavement performance. © 2015 American Society of Civil Engineers.